Why is this object completely black while in edit mode?
In this case mesh is built with too many vertices and faces serving no purpose for this not complex mesh. Initially it has slightly more than ~2000 polygons which is too much for that.




Select all with A, press W > Remove doubles. It will tell you that around 2000 double vertices was removed.
Select all if not selected and press Ctrl+N to recalculate normals. The model will look as usual from now on.




Read about normals: Why are some of faces in my mesh darker